Automatic piston stroke compensator for free piston engines



Feb. 14, 1950 w. A. MORAIN E'rm. 251979091 AUTOMATIC PISTON STROKE COMPENSATOR FOR FREE PISTON ENGINES Filed June 14, 1945 2 sneet wsneat 1' WZLAJJ A.MUHAIN PAUL .51 51mm? Feb. 14, 1950 w A MORAIN ETAL 2,497,091

AUTOMATIC PI STON STROKE COMPENSATOR FOR FREE PISTON ENGINES Filed June 14, 1945 2 Sheets-Sheet 2 Im-E- I ViLLAED AMURAIN PA UL 5i EHJHLEY awe/WM v Patented Feb. 14, 1950 AUTOIVIA'IIC PISTON STROKE COMPENSA- TOR FOR FREE PISTON ENGINES Willard A. Morain and Paul S. Shirley, Hamilton, Ohio, assignors, by mesne assignments, to Lima-Hamilton Corporation, Hamilton, Ohio, a corporation of Virginia Application June 14, 1945, Serial No. 599,478

27 Claims.

This invention relates to internal combustion engines of the free piston type, and particularly to automatic means to control the fuel feed in accordance with predetermined running conditions of the engine.

In the efficient and economical operation of engines of this type, a control or governor is needed which will limit the fuel injected per stroke to that necessary to reach the maximum desired stroke of the pistons under varying load conditions.

It is found in practice in the operation of free piston internal combustion engines that the desirable stroke length of the pistons varies under varying load conditions and that while, for instance, the desirable stroke length under maximum load conditions may be ten inches, this may be reduced under idling to, for instance, nine inches. For efficient and economical running under such conditions, it has heretofore been necessary to manually adjust the fuel feed to suit the varying requirements.

An object of the invention is the provision of means to automatically compensate for overstroke conditions in the running of a free piston engine, which means is operable by an overstroke of the pistons, preferably at the ends of their working strokes, to effect a fuel feed adjustment whereby the quantity of fuel charges is reduced, temporarily at least, to return the engine to normal stroke conditions and to vary, in accordance with the load upon the engine, the point at which the overstroke control becomes effective.

Another object of the invention is the provision in an engine of the character described, of stroke compensating means which is efficiently operable under both maximum and idling or light load conditions to correct overstroke of the pistons and which accomplishes this automatically through the medium of certain resulting pressure changes, for instance the exhaust receiver gas pressure of the engine.

The invention is fully described in the following specification, and one embodiment thereof illustrated in the accompanying drawing, in which- Fig. 1 is a schematic arrangement of a mechanism embodying the invention in operative association with a free piston engine; Fig. 2 is an enlarged schematic arrangement of the parts which cooperate in the functioning of the invention; Fig. 3 is a central longitudinal section of the secondary fuel feed control unit of such mechanism; Fig. 4 is a sectional detail of a simple form of fuel injection pump; Fig.5'is a modification of the overstroke control valve and its operating means, and Fig. 6 is a perspective view of the control valve.

Referring to the drawings, I designates an internal combustion free piston engine including opposed piston sets, each comprising a working piston 2 operating in a combustion chamber 3, an air compressor piston 4 operating in a chamber 5 and a direct bounce piston 6 operating in a chamber 1, all for the purpose and in a manner understood in the art.

For the purpose of synchronizing the movements of the piston sets, a rack-bar 8 projects inwardly from one set of pistons and a rack-bar 9 projects inwardly from the other set through the inner end wall of the respective chamber 5 and in laterally spaced parallel relation at a side of the cylinder l0 forming the combustion chamber 3. These rack-bars mesh with a pinion II disposed therebetween and mounted on a stub shaft l2 projecting from the engine casing substantially midway of the ends of the cylinder Ill.

The engine operates on a cycle somewhat analogous to a conventional two stroke cycle. On the outward or working strokes of the pistons air is compressed in the cylinder 5 by the pistons 4 and is discharged therefrom into a scavenging receiver l3 which has communication with the combustion chamber to admit scavenging air thereto when the pistons are approximately at the ends of their working strokes. The exhaust gases and scavenging air in the combustion chamber 3 are discharged therefrom when the pistons are near the end of their working strokes, and such discharged gases are directed into an exhaust receiver l4 by a conduit (not shown) for use in a turbine or otherwise. It is apparent that the exhaust gas pressure in the receiver It varies with the engine load in normal operation and that the greater the load the greater is such pressure, and that when the engine is idling this pressure drops.

Fuel is supplied to the combustion cylinder 3 of the engine from an injector pump 15 to which fuel is supplied through a pipe line l6 (Fig. 2) from a constant pressure fuel pump 1'! and is ejected from the pump through a line I8 leading to-the customary injection nozzle (not shown). The pump receives its supply of oil from a tank I9 or other suitable source of supply. The injector pump 15 is of the plunger type, and its plunger 20 is provided at its outer end with a roller 2| that rides on one of the-synchronizing rack-bars, 9 in the present instance, and is actucited to eject a fuel charge when the roller travels up a cam 22 on such bar. This engagement is customarily timed to take place just before the working pistons have reached the ends of their inward or compression strokes. The pump plunger 20, in addition to being reciprocably movable in the pump casing to force a fuel charge from the pump, is also rotatable about its longitudinal axis whereby a controlled metered charge of fuel is admitted to the charge chamber of the pump during each stroke cycle of the plunger, due to a spiral feature of the plunger, the charge being increased when the plunger is turned in one direction and reduced when turned in the other direction, as well understood in the art. Rotary adjustment of the plunger 20 to vary the fuel feed is effected by longitudinal movement of a rack-bar 23 in engagement with a pinion on the plunger, as is common in the art. Inasmuch as the specific form of the fuel injector pump forms no part of the present invention, it need not :be more fully described.

For the purpose of the present embodiment of the invention, a movement of the rack-bar 23 to the right effects a reduction in the quantity of fuel injected at each pump stroke, while a movement of such bar to the left effects an increase in the quantity of a pumped fuel charge.

The present invention comprises an automatic control mechanism for the rack-bar whereby the quantity of fuel feed is varied so as to control any overstroke of the engine pistons by necessary reduction of the fuel charges. This mechanism, in the present embodiment of the invention, includes a primary control for the fuel feed which may be set manually for any load condition, together with a secondary control therefor, which is connected to and is operable by movement of the engine pistons at the outer ends of their strokes to reduce the fuel feed when an overstroke condition occurs. Such mechanism also includes an additional control feature operating in conjunction with said secondary feature which is automatically adjustable to insure a proper idling operation of the engine and a correction of any overstroke during such operation as well as controlling all running conditions during power output operations.

The primary control means, which will first be described, is the same as disclosed and claimed in a co-pending application, Serial No. 761,173, filed July 16, 1947, in the name of Frank M. Lewis in connection with a different type of automatic overstroke control wherein a mechanical means actuated by an overstroke of the piston in cooperation with the fuel feed line pressure is utilized to compensate for stroke variance.

The primary control means, which is designated A in the drawing and is shown in sectional detail in Fig. 3, includes a casing 25 having an elongated cylinder bore 26 open at its outer end and preferably abruptly reduced in diameter at its inner or closed end portion to form the shoulder 21. A rod 28 fixedly projects from an end of the rack-bar 23 into the bore 26 through its open end and is provided at its free end with a piston 29, slidingly fitting into a cup-like dash-pot plunger 30, operating in the small inner end portion of the bore to form a chamber 31 therein. A guide sleeve 32 is slidingly mounted in the outer end portion of the bore 26, and has a restricted outer end portion slidingly engaging the rod 28 and in outward stop coaction with a fixed collar or enlargement 33 on the rod. A cross-member 34 is slidingly mounted on the rod 28 to engage the reduced end portion of the sleeve 32 in opposi- 75 stroke of the valve.

4 tion to the stop 33 and is acted on by a coiled compression spring 35 to yieldingly hold the reduced sleeve portion to said stop. The spring 35, in the present instance, encircles the rod 28 with its inner end thrust against the piston 29. The cross-member 34 has arms projecting outwardly through registering side slots 36 and 31 in the sleeve 32 and casing 25, respectively, and one of these arms has a connection 38 with a manual control lever 39. This lever is mounted on a convenient part of the engine frame and carries a hand latch 40 in engagement with a toothed sector M to permit manual control of the rack-bar 23 when desired. The plunger 36 is urged to the right and against the piston 29 by a spring 42 in the chamber 3|, such spring being of insufificient strength to overcome the tension of spring 35 and move the rack-bar 23 to the right or in fuel charge reducing direction.

A trip sleeve 44 is mounted in the large portion of the bore 26 at the inner side of the guide sleeve 32 in spaced relation thereto, and has an inward enlargement at its outer end forming an internal shoulder 45 and a peripheral recess 45, with the inner or left hand wall of such recess preferably tapered to form a slight undercut. A heavy spring 41 is compressed between the bore shoulder 2'! and sleeve shoulder 45. A trip lever 48 of bell crank form is fulcrumed to a convenient part of the casing 25 and has one arm provided with a catch finger 49 adapted to project through the casing slot 31 and have catch engagement with the undercut side of the recess 46 to hold the sleeve 44 in retracted spring compression position, as shown in Fig. 3. Upon a release of the catch sleeve, it is quickly moved outward by its spring and caused to strike the inner end of the guide sleeve 32 and move it, together with the rod 28 and its connected parts, outward to fuel stop position to stop the running of the engine. A spring acts on the trip lever to yieldingly hold it in catch engagement with the sleeve. Any desired emergency control means can be provided to operate the trigger 48. As such emergency means forms no part of the present invention, it will not be shown or described herein.

Oil, in the present instance, under fuel line pressure, is supplied to the chamber 3| through branch lines 50, 5|, from the supply line IS. A control valve 52 constituting a part of said secondary control and which is of the plunger type, is disposed between branch lines and operates to open the connection therebetween under predetermined operating conditions. This valve includes a casing 53 having a bore 54 therein in which a plunger 55 is mounted for both longitudinal reciprocatory movements and rotary movements about its longitudinal axis. This plunger is provided intermediate its ends with a half circumferential relief recess 55, one end wall of which is circumferentially inclined to form an oblique helix 5'! extending substantially half around the plunger, as best shown in Fig. 6. Both of the oil feed line branches 5i] and 5! open into the bore 54. The oil feed line is preferably in permanent communication with the valve recess 53 while the branch Si is in communication with such recess and with the branch 50 only when the valve is at or near the outer end of its stroke. Such time of opening of the communication between the branches 58 and 5! is varied by a rotary adjustment of the valve so that the helix 5'! will act to open said communication earlier or later in a For instance, if the long side of the bodyportion of the valve plunger at the helix is in register with the branch 5|, such branch will remain closed during a normal stroke length of the plunger which is controlled by the piston strokes, as hereinafter described, but will open upon an overstroke condition of the pistons.

The time of opening of the branch 5| to the valve recess 55 may be shortened relative to the stroke length of the pistons by a rotary adjustment of the valve so that the branch 5| will be uncovered by an intermediate portion of the helix 51. I

In the present instance, the plunger 55 is driven by and caused to reciprocate in unison with the pistons, but at a reduced motion, by connecting the outer end of the valve to a rack segment 58 that is fulcrumed at 59 to a convenient part of the engine frame and has its toothed edge in mesh with a pinion 60 on the shaft |2 of the piston synchronizing means. The outer end of the plunger 55 is engaged by a rotatable head 6|, and this head is connected by a link 62 to the segment 58.

For the purpose of rotating the plunger 55 so as to cause an early or late opening of the branch line 5|, a sleeve 63 is rotatably mounted in the valve casing 53 in splined engagement with the plunger and this sleeve is provided with a pinion 64 that is exposed at one side of the casing 53 and is in engagement at such point with a rackbar 65. This rack-bar projects from a piston 66 operating in a cylinder 61, one side of the piston 66 being exposed to exhaust receiver pressure through a communicating line 68 and its other side being engaged by an expansion spring 69. The communication of the line 68 with the interior of the exhaust receiver I4 is controlled by a needle valve H1 and also by an outwardly opening check valve H. The check valve permits a rapid communication of pressure from the exhaust receiver to the cylinder 61 while the nozzle Valve 'lll restricts the back flow of pressure from the cylinder to the exhaust receiver, thus serving to utilize substantially the maximum gas pressure in the receiver. The tension of the spring 69 is such that under normal maximum load conditions the exhaust receiver pressure will move the rack 65 and its piston 66 out a sufficient extent to hold the plunger 55 in such a position that the tip of the valve helix 5! is somewhat short of longitudinal register with the branch line 5| so that a higher than normal exhaust pressure will be permitted to take place to meet overload conditions. When the engine is idling the gas pressure in the receiver l4 and in the cylinder 61 is accordingly lowered, so that the plunger 66 will be forced inward a distance by the spring 69, thus positioning the valve helix 51 to cause an earlier opening of the branch line 5| to take place than would be the case if the pressure in the receiver I4 was up to normal. The valve plunger 55 is thus automatically set for a shorter stroke corresponding to the idling stroke ofthe engine pistons and any overstroke during such idling will be corrected the same a when operating under normal load conditions.

Upon an overstroke movement of the engine pistons, which is ordinarily occasioned by too great a fuel feed for the engine load existing at the time, the synchronizing pinion II is moved a greater distance in clockwise direction than normally, thus increasing the movement of the gear segment 58 to the left and imparting a longer outward stroke to the valve plunger 55, so as to uncover the branch 5| during a portion of the plunger stroke and permit fuel oil to feed to the control chamber 3| through branch pipe 5|. This action, as is apparent, moves the rack-bar 23 of the fuel ejector I5 to the right and reduces the quantity of fuel feed. This reduction in fuel feed is continued until the engine stroke is reduced and normal speed running effected. The position of maximum engine stroke can be controlled by adjustment of the tension of the spring 69, or of turn buckle 12 on link 62. These adjustments and the position of the valve helix 51 should be such that for a normal maximum stroke of the engine pistons the valve plunger 55 will remain in closed relation to the feed branch 5|, while for a longer stroke it will be moved to open the line 5| to admit oil feed line pressure to the chamber 3|.

A needle valve 15 (Fig. 3) controls leakage of oil from chamber 3| through a passage 16 leading to and through a drainage line 11 to the oil supply tank IS. The rate at which the fuel injection of the pump l5 can be increased by movement of the plunger 28 and connected rack-bar 23 to the left is limited by the compression in spring 35 and the size of the opening through which the oil can leak past valve 15. A relief port 18 is provided in the side wall of the chamber 3| in communication with the branch line 11 and in position to be uncovered by the plunger 30 when it has moved a predetermined extent to the right or in fuel reducin direction from normal running position, thus relieving pressure in chamber 3| and permitting spring 35 to act to return the plunger to port closing position. This acts, as is apparent, to continue a running of the engine under substantially uniform reduced fuel condition until the fuel feed has been increased to meet operating requirements.

The operation of the apparatus is as follows. When the engine has been started, it is set for the desired running speed by adjustment of the hand control lever 39. Movement of the lever to the right reduces the fuel feed for slowrunning and movement to the left increases the fuel feed for faster running. The rate of automatic fuel injection increase is limited, of course, by the rate of oil leakage from the chamber 3| through the line Tl relative to the amount of oil pressure supply to such chamber. The rate of fuel increase to the engine from the pump I5 is thus made controllable and the disturbances resulting from a too sudden opening movement of handle 39 can be avoided. During normal running of the engine the helical land of plunger 55 at the end of recess 56 is in line with the opening into pipe 5| and uncovers that opening only when the stroke of the engine is abnormally long. When the engine stroke is continued beyond the normal limit at the scavenging end of the stroke, the movement of plunger 55 to the left is continued until recess 56 communicates with pipe 5| and admits fluid under pressure to chamber 3|. Thereupon the fluid in chamber 3| overcomes the pressure of spring 35 sufllciently to move parts 30, 29, 28 and 23 to the right and reduce the charge of fuel. The supply of fluid under pressure to pipe 5| continues at each stroke of the engine until the fuel is sufficiently reduced to remedy the overstroke condition. The plunger 30 uncovers relief opening 18 before the fuel is entirely shut oil, and so suflicient fuel feed is continued to prevent stopping the engine. When overstroke conditions are remedied, the flow of fluid to chamber 3| is cut off and spring 35 gradually forces fluid out through needle valve 15 to return the fuel feed memos to the normallamount'. However, when thepressure in chamber [4' is reduced, the pistonstend.

to overstroke. The reduced pressure in chamber 61 is then overcome by Spring 69. suflicientl'y to turn plunger 55' to a position where the oblique wall 5'! is in line with the opening into pipe 5|. This renders the overstroke remedying mechanism operative upon a shorter stroke so that the than is desirable under the conditions of such increased pressure.

In the construction. described, the engine is intended for supplying gases under pressure to the exhaust receiver. Under such circumstances the pressure in the exhaust receiver substantially determines the load upon the engine. If the engine was intended to compress air for other purposes so that part or all of the compressed air was used otherwise than for scavenging the engine, the pressure against which the engine worked, and therefore the load upon the engine, might be determined by the pressure in a chamber receiving gas from the compressor, and connection with such gas receiver might be substituted for the connection to the exhaust receiver indicated in the illustrated construction.

It is apparent that the present overstroke control is at least partly pneumatic in its action and makes use of the relation between the piston stroke of the engine and the exhaust gas pressure in receiver M, and that the control of the movement of the valve rack 65 serves to govern the valve plunger stroke at which the port to the branch oil line 5! is uncovered. It is also apparent that by suitably proportioning the area of the piston 65 and the spring reaction thereon, and by selecting the proper helix form for the valve plunger 55, the overstroke limit control can be made to follow the desired load curve or any other desired characteristic.

Obviously other constructions, one of' which is illustrated in Fig. 5, might be employed for automatically reducing the fuel charge under overstroke conditions, and the same principle might be employed by which the overstroke remedying I mechanism operates with one length of stroke under normal conditions and operates to limit the stroke to a shorter length when the load upon the engine is reduced, limiting it to a minimum when the engine is idle.

In Fig. 5, one of the rack-bars 8, 9, the former in the present instance, is provided at its outer end with a cam 80 having a prolonged slope for. engaging a roller on a plunger 8| at'the end of an outward or working stroke of the pistons, particularly on an overstroke. The plunger 8ll is reciprocably mounted in a valve case 82 in'theopen end of its bore 83 and acts through a compression spring 84 on a valve piston 85 operating in the bore and in opposition to a spring 86. This piston normally closes the communication between branch oil feed lines and 5] corresponding to the lines 50 and 5% of the previous form. An exhaust pressure line 68, corresponding to the line 58 of such first form, opens into 8: the cl'osed'end of' the bore 83 so that: exhaust gaspressure from the receiver cooperates with the spring 86'to oppose movement of the piston under pressure of" the spring 84'. The piston 85 normall'ycloses the branch 50 and upon adownward movementof the piston under the action of the spring 84 opens-said branch tothe branch 51-, wherebypressure' is admitted to the chamber 3lto effect reduction of' the fuel feed. When cam depresses plunger 8|, the spring' M- is compressed andltends-to lower piston against both gas pressure from line 68 and pressure from spring 86. The amount of' gas pressure from line 68' determines how muchspring 81 must be ;compressed before piston 85 has uncovered branch line 50', and so d'eterminesatwhat point on slope of cam 80 connection is madebetween branches 5!! and 5|. The spring 86 is required to position piston 85 during periods when gas receiver pressureis atmospheric. Spring'84 may be of such normal length that it may be fully extended in the operation shown and compressed only as plunger Si is moved downward by cam 80. It is apparent that at the outer end of each piston stroke the cam 80 will move more or less over the plunger roller depending on the length of the stroke, and the time of openin of the oil pressure line 50', 5|, relative tothe piston stroke, will depend on the pressure opposing, the opening movement of the piston. Accordingly, if the engine is idling, the receiver gas pressure is relatively low so that a less inward movement of the plunger 8 i. on an overstroke of the pistons will efiect an opening of the valve piston 35- than when the engine is operating under full load condition, and agreater. movement of the plunger 8| is required to open the valve upon an, overstroke under such conditions. The piston 85 is provided with one or more. peripheral. grooves; 81

adapted to register, indifferent positionsv oi the piston,.with a branch port 88 inthe. cylinder wall.. This prevents leakage of oil. from the chamber holding. the spring, 85 and also. from. the line 50- to pass along the piston and into the chamber holding the spring 86.

We wish it. understood that the inventionis 'not restricted to any particularv construction; arrangement or form of the-parts, as. it. is capableof numerous modifications and changes without departing'from the spirit of the claims, the essential-featurebeing that the fuel charge is automatically varied when the'exhaust receiver pres sureis varied soas to allow full stroke for the particular load conditions but to prevent overstroke.

Having thus described: our invention, what we. claim asnew, and desire to secure by United. States Letters-Patent, is'::

1. In: an' internal. combustion engine of the free piston type, an adjustable fueli feed, automatic stroke-limiting means operable by movement of the pistons beyond a predetermined stroke to reducethe fuel feed ateach' stroke until there: isno longer an overstroke, and automatic means for adjusting, in accordancewith the load on the engine, the length of the stroke which renders said limiting means operative.

2. In an internal combustion engine of the free piston type, an adjustable fuel feed', means, actuated b movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer move beyond said predetermined" scavenging position, and means. forvarying' said predetermined scavenging position in accordance with the load on the engine.

3. In an internal combustion engine of the free piston type, an adjustable fuel feed, means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer move beyond said predetermined scavenging position, and means responsive to the load on the engine for shortening said scavenging position as the load is decreased below normal and lengthening it as the load is increased to normal.

4. In an internal combustion engine of the free piston type having a gas pump run by the engine and a chamber receiving gas from the pump, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer travel beyond said scavenging position, and means controlled by the pressure in said chamber for predetermining the position of the pistons at which said limiting means becomes operative.

5. In an internal combustion engine of the free piston type having a gas pump run by the engine and a chamber receiving gas from the pump, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer travel beyond said scavenging position, and means controlled by the maximum pressure in said chamber at each stroke of the engine to predetermine the position of the pistons at which said limiting means becomes effective.

6. In an internal combustion engine of the free piston type having a gas pump run by the engine and a chamber receiving gas from the pump, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer travel beyond said scavenging position, and means actuated by the fall of pressure in said chamber below normal to shorten the stroke of the pistons at which said limiting means becomes effective.

'7. In an internal combustion engine of the free piston type having a gas pump run by the engine and a chamber receiving gas from the pump, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer travel beyond said scavenging position, a member controlling the length of the stroke of the pistons at which said limiting means becomes operative, resilient means pressing said member in one direction and said member being pressed in the opposite direction by gas from said chamber.

8. In an internal combustion engine of the free piston type having a gas pump run by the engine and a chamber receiving gas from the pump, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer travel beyond said scavenging position, a piston exposed on one side to gas from said chamber, a spring urging said last piston against said gas pressure, and connections varying the position of the engine pistons at Which said lim- 10 iting means becomes effective in accordance with the position of said spring urged piston.

9. In an internal combustion engine of the free piston type having a gas pump run by the'engine and a chamber receiving gas from the pump, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel feed at each charge until the pistons no longer travel beyond said scavenging position, a piston exposed on one side to gas from said chamber, a spring urging said last piston against said gas pressure, and connections shortening the stroke of the pistons at which said limiting means becomes effective when said spring urged piston is moved by the spring beyond a normal position.

10. In an internal combustion engine of the free piston type operating a gas pump and discharging the gas pumped and the exhaust gases into an exhaust receiver, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel charge at each stroke until the pistons no longer travel beyond said position, and means controlled by the pressure in the exhaust receiver to determine the position of the pistons at which said limiting means becomes effective.

11. In an internal combustion engine of the free piston type operating a gas pump and discharging the gas pumped and the exhaust gases into an exhaust receiver, an adjustable fuel feed stroke-limiting means, actuated by movement of the pistons beyond a predetermined scavenging position, to reduce the fuel charge at each stroke until the pistons no longer travel beyond said position, and means, rendered eflective by the fall of pressure below normal in the exhaust receiver, to render said limiting means effective upon a shorter stroke of the pistons than is normally required to render said limiting means effective.

12. In an internal combustion free piston engine, including a fuel injection means adjustable to increase or decrease the quantity of the fuel charges, a control for said injection means normally operable by spring pressure to increase the quantity of the fuel charges and by fluid pressure to decrease such charges, a fluid pressure line for supplying pressure to said control, and valve means connected to and reciprocable at reduced motion with the engine pistons and maintaining said line closed under predetermined normal stroke conditions of the engine and opening said line upon an overstroke condition of the pistons.

13. In an internal combustion free piston engine, including a fuel injection means adjustable to increase or decrease the quantit of the fuel charges, an automatic fuel feed control for said injection means, said control being normally operable to increase said feed and operable by predetermined fluid pressure to decrease said feed, a fluid pressure line for supplying fluid pressure to said control to decrease the fuel feed, a longitudinally reciprocable plunger valve for said line, connection between the valve and engine pistons to cause the valve to reciprocate with the pistons at reduced motion and maintaining said line closed under normal maximum operating condition of the engine, and operating to open the line at the outer end of each overstroke of the pistons.

14. In an internal combustion free piston en- 11 gine, including a fuel .injection means adjustable to increase or decrease the quantity of fuel charges, an automatic fuel-feed control for .said injection means, said control being normally operable to increase said feed and operable in opposition thereto by predetermined .fluid pressure to decrease said feed, a line for supplying fluid under pressure to said control to act to decrease the fuel feed, valve means disposed in .saidline and having a movable valve member connected to the engine pistons and reciprocable at reduced motion in synchronism with the pistons, said valve means operating to maintain said line closed under predetermined normal operating stroke conditions and to open the line to admit fluid line pressure to said fuel feed control.

.-15..In an internal combustion free piston engine, including afuel ilnjector means adjustable to increase or reduce the fuel charge for each injection, and an exhaust gas receiver, -mechanism connected to the fuel injection .means and operable to adjust said means to increase or decrease its fuel charge and responsive to fluid pressure to :adjust said means to reduce the fuel charge, and means responsive to a predetermined overstroke running condition of the engine and to a predetermined increase :of gas pressure above normal in said receiver to con- .trol the admission of fluid pressure to said mechanism to actuate .it to adjust said injection means to reduce the fuel charge until said condition is corrected.

16. An arrangement as called for in claim 4 wherein the second-mentioned means includes a fluid pressure line to said .limiting means, a valve in said line connected to and movable .in accordance with the engine piston movements to open and close said line, andmeans responsive to the exhaust receiver gas .pressure to adjust said valve to vary the opening of said line .a predetermined extent relative to the .movements of the engine pistons to open said line under predetermined abnormal operating conditions of the engine.

17. An arrangement as called for in claim 4 .wherein the second-mentioned .means includes a fluid pressure line to said limiting means a plunger type valve having a recess with an oblique helix wall for opening and closing said line, said valve being movable both longitudinally androtatably relative to its axis, connection between the valve and engine pistons to .move it longitudinally at reduced motion inunisontherewith, and means operable by receiver gas pressure to rotatably adjust said valve to change its helix position relative to said line to effect ,an earlieropening thereof upon the increase of a predetermined normal pressure in said receiver, said line remaining closed by the valve except when an overstroke condition .of the engine pistons or a gas pressure above normal is present insaid receiver.

18..In an internal combustion engine of the free piston type, including a fuel injection means adjustable to increase or decrease the fuel charge for each injection, a synchronizing means for the engine pistons, and an exhaust receiver, mechanism connected to the fuel injectionmeans and operable by fluid pressure to decrease its charge, a fluid pressure line tosaid mechanism for .said purpose, .a valve associated with said line and having connection with and operable by said synchronizing means to have stroke movements corresponding to and in unison with :12 the engine pistons and to open said line only when other than predetermined normal working conditions of the engine-are present, and means responsive to pressure in said receiver and operable to rotatably adjust .said valve to effect an earlier than normal opening of said line when the receiver pressure is above a predetermined normal maximum.

19. In an internal combustion engine of the free piston type, including a fuel injection means adjustable .toincrease or decrease the fuel charge for each injection, asynchronizing means for the engine pistons and an exhaust receiver, mechanism connected to the fuel injection means and operable by fluid pressure to decrease its charge, a fluid pressure line .to-said mechanism for said purpose, a valve associated with said line and having connection with and operable by said synchronizing means to have stroke movements corresponding to and in unison with the engine pistons and .to open said ,line only when other than predetermined normal working conditions of the engine are present, means responsive to pressure in said receiver and operable to rotatably adjust said valve to effect an earlier than normal opening of .said .line when the receiver pressure is above a predetermined normal maximum, andmeans yieldingly opposing adjustment of the valve by said gas pressure.

20. In aninternal combustion free piston engine, including a fuel injection means adjustable to increase or decrease the quantity of the fuel charges, and .an .exhaust gas receiver, ,a control for said injectionmeans-operable .by fluid pressure to decrease the fuel charges, a fluid pressure line for supplying pressure to said control for said purpose, valve .meansconnected to and reciprocable at reducedmotionwith the engine pistons and maintaining said line closed under predetermined normal stroke conditions of the engine and opening said line ,upon an overstroke condition of the pistons, and means having connection'with said valvemeans and responsive to gas pressure in said receiver to adjust said valve means to effect an earlier or a later opening of said line'by the valve :means for each engine piston stroke depending on predetermined operating conditions.

21. In an internal combustion free piston engine, including a-fuel injection means adjustable to increase or decreasethe quantity of the fuel charges, and an exhaust gas receiver, an automatic fuel feed control forsaid injection means, saidcontrol being normally operable to increase said feed and operable by predetermined fluid pressure to decrease said feed, a fluid pressure line for supplying-fluid pressure to said control to decrease the fuel feed, a valve'for said'line having connection with the engine piston for reduced-motion :movements corresponding thereto, said valve normally maintaining said line-closed and operating to open it upon an overstroke movement of the pistons to admit fluid pressure to said control .toreduce'the fuel'feed, and means responsive toan increase 'in pressure over a predetermined :maximum'nor-mal in said receiver to adjust said valve for an earlier opening of said line-by the valve independently ofthe length of its piston actuated strokes to cause the control to varythe fuel feed to'return the receiver pressure to the maximuminormal.

22. In an internal combustion free piston engine,.including afuel injection means adjustable to increase or decrease the quantity of the fuel charges, and an exhaust gas receiver, an automatic fuel feed control for said injection means, said last means being normally operable to increase said feed and operable by predetermined fluid pressure to decrease said feed, a fluid pressure line for supplying fluid pressure to said control to decrease the fuel feed, a longitudinally reciprocable plunger valve for said line, connection between the valve and engine pistons to cause the valve to reciprocate with the pistons at reduced motion and maintaining said line closed under normal maximum operating conditions of the engine and operating to open the line at the outer end of each overstroke of the pistons, said valve being rotatably adjustable and having a helix feature which upon rotation of the valve varies the time of opening of said line relative to the piston strokes, and means having connection with and controlled by pressure in said receiver to impart predetermined rotary adjustment to said Valve upon a change of receiver pressure.

23. In an internal combustion free piston engine, including a fuel injection means adjustable to increase or decrease the quantity of fuel charges, an automatic fuel feed control for said injection means, said last means being normally operable to increase said feed and operable in opposition thereto by predetermined fluid pressure to decrease said feed, a line for supplying fluid under pressure to said control to act to decrease the fuel feed, valve means disposed in said line and having a movable valve member connected to the engine pistons and reciprocable at reduced motion in synchronism with the pistons, said valve means operating to maintain said line closed under predetermined normal operating stroke conditions and to open the line to admit fluid line pressure to said fuel feed control to effect a decrease in the fuel feed charges when an overstroke operating condition of the engine pistons is present, said valve means being adjustable, and means automatically operable by a running of the engine to adjust the valve means to effect an earlier opening of said line relative to the stroke length of the engine pistons to cause said control to reduce the fuel feed when an overstroke of the pistons occurs for a predetermined set condition of running.

24. In an internal combustion free piston eng-ine, a set of free pistons, a fuel injection means adjustable to increase or decrease the fuel charge for each injection, and mechanism including cooperating spring means and fluid pressure responsive means operable to act on said injection means to reduce the fuel charges when a predetermined overstroke running condition of the engine is present, said mechanism also including a fluid pressure line, a valve connected to the engine pistons for reduced synchronized movements therewith and operable thereby to maintain said line closed under normal stroke length operation of the piston and to open said line to admit fluid pressure to said responsive means to cause a reduction of the fuel charges when an overstroke condition of the pistons occurs.

25. An arrangement as called for in claim 12 wherein said line closing means is adjustable to suit changes in a normal stroke running of the pistons under changed load or idling conditions, and means responsive to a variance in a predetermined gas generated pressure of the engine to effect the adjustment of said line closing means.

26. In an internal combustion engine having free pistons, an exhaust gas receiver, and a fuel feed means, a movable member in connection with said means, spring means acting to move said member in feed increasing direction, a fluid pressure dash-pot opposing said spring movement and operable by increase of pressure therein to move the member in feed decreasing direction, a line for supplying fluid pressure to the dash 'pot, a valve normally closing said line and having connection with and operable by the pistons to open said line to admit fluid pressure to the dash-pot upon an overstroke of the pistons, said valve being adjustable to vary the time of opening of the line to suit a changed normal stroke condition of the pistons, and means controlled by a change of pressure in said receiver to suit the load or idling condition under which the engine is operating.

27, An arrangement as called for in claim 15 together with means automatically operable during a running of the engine to adjust said responsive means to take care of an overstroke of the pistons for any normal running condition of the engine for which set.

WILLARD A. MORAIN. PAUL S. SHIRLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,064,976 Janicke Dec. 22, 1936 2,083,680 Anderson et a1 June 15, 1937 2,139,425 Steiner Dec. 6, 1938 2,200,892 Pescara May 14, 1940 

